In mobile telecommunications networks, there is a requirement for User Equipment (UE) to handover from one base station to another. In the 3GPP, there has been recently proposed a procedure defined in the control plane (C-plane) for handover (HO) from a source eNodeB (base station) to a target eNodeB. The various acronyms applicable to 3 G communications will of course be familiar to those skilled in the art but a glossary is appended for the benefit of lay readers.
Although for efficiency of understanding for those of skill in the art the invention will be described in detail in the context of a 3 G system, the principles of handover can be applied to other systems, e.g. other CDMA or wireless in which a mobile device or User Equipment (UE) communicates with one of several other devices (corresponding to eNodeB) with the corresponding elements of the system changed as required. At the RAN2/RAN3/SA2 joint meeting in St. Louis, the SAE/LTE architectural principles were agreed and the decision was to move the PDCP layer down to the eNodeB (base station). At the following RAN2 meeting in Malta it was decided that the ciphering would be performed at the PDCP layer using PDCP Sequence Numbers. Based on this decision user plane handling during handover needs further consideration and the present application proposes a suitable handover procedure.